Gear pump



April 14, 1964 o. c. BLOMGREN ETAL 3,

GEAR PUMP Filed Sept. 19, 1960 4 Sheets-Sheet 1 INVENTORS! OSCAR C. BLOMGREN OSCAR C. BLOMGREN, JR. 71 Mw ATT'YS April 1964 o. c. BLOMGREN ETAL 3,128,710

' GEAR PUMP Filed Sept. 19, 1960 4 Sheets-Sheet 2 INVENTORS: OSCAR C. BLOMGREN OSCAR C. BLOM GREN, J R.

ATT'YS April 4, 1964 o. c. BLOMGREN ETAL 3,128,710

GEAR PUMP Filed Sept. 19, 1960 4 Sheets-Sheet 5 FIG. 6 I

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INVENTORS: OSCAR C. BLOMGREN OSCAR C. BLOMGREN,JR.

April 14, 1964 o. c. BLOMGREN ETA L 3,128,710

GEAR PUMP Filed Sept. 19, 1960 4 Sheets-Sheet 4 FIG.||

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INVENTORS: OSCAR C, BLOMGREN OSCAR C. BLOMGREN JR.

I BY 65%165? ATT'YS United States Patent 01 Patented Apr. 14, 1964 ice 3,128,710 GEAR PUMP Oscar C. Biomgren, 472. Lincoln Ave, and Oscar C. Blomgren, .lr., 23? Park Lane, both of Lake Bind, Ill.

Filed Sept. 19, 196i), Ser. No. 56,833 12 Claims. (Cl. l0342) This invention relates in general to a gear pump and more particularly to a positive displacement gear pump. While the pump may be constructed of any desirable types of materials, one of the features of the invention is in constructing the pump primarily of plastic, and particularly a plastic known as Delrin which is as tough as most metals and has low frictional features and dimensional stability.

The pump of the present invention includes a body having upper and lower symmetrical cavities for receiving the coacting drive and idler gear and bearing assemblies in cartridge arrangement. The idler and driven gears and associated bearings may be interchangeably located in either of the cavities thereby permitting a versatility and flexibility of operation. Front and back covers are secured to the opposite sides of the body including the cavities and may also be interchangeably mounted in order to accommodate any particular desired installation. The drive shaft carrying the drive gear extends through the front cover and is mechanically sealed relative thereto. A by-pass assembly is integrally arranged on the rear cover and capable of improving the performance and operation of the pump. Because of the construction of the body and the cartridge type gear and bearing assemblies, the pumps may be arranged in tandem to provide other applications thereof.

Accordingly, it is an object of this invention to provide an improved gear pump having its components so symmetrically constructed as to enable wide flexibility in usage for a great number of particular applications.

Another object of this invention resides in the provision of a positive displacement gear pump having components symmetrically constructed in order to permit the pump to be connected and used in multiple.

One particular feature of the invention is in the by-pass assembly which is integrally constructed in one cover of the pump. Therefore a further object of the invention resides in the provision of an improved by-pass assembly for a positive displacement gear pump which is simple in construction and inexpensive to manufacture.

A still further object of the invention is to provide a positive displacement gear pump having a by-pass assembly capable of handling the full normal capacity of the pump, wherein quieter operation and low heat rise is obtained.

A further object of the invention is to provide a by-pass assembly for a positive displacement pump wherein the assembly and pump are so symmetrically constructed as to permit easy and quick changing of the by-pass assembly to opposite sides of the pump.

Another object of this invention is in the provision of a by-pass assembly for a gear pump having a single control for adjustment of by-pass pressure and for shut oil" of the by-pass.

Still another object of the invention resides in the provision of a by-pass assembly for a positive displacement gear pump wherein only a single by-pass may be efiectively employed in connection with multiple pump assemblies.

Another feature of the invention is in the construction of the pump components which permits easy and quick maintenance of a pump thereby reducing shut down time.

Another object of the invention is to provide a positive displacement gear pump having O-ring gasketing thereby eliminating the necessity of replacing gaskets after any disassembly of the pump.

A further object of the present invention resides in the provision of a so symmetrically constructed gear pump that multiple pump assemblies may be interconnected to provide mixing units for mixing fluids and the like.

A still further object of the invention is to provide a pump constructed primarily of plastic, wherein a liner may be employed to enlarge on the usage of the pump, and in which case the plastic body of the pump is molded around the liner.

A still further object of the present invention resides in the provision of a pump primarily constructed of Delrin wherein no lubrication is needed.

A still further object of the present invention is to provide gears for a positive displacement gear pump that are constructed to prevent pressure lock during operation of the pump.

Another object of the invention is to provide a positive displacement gear pump employing the pumping fluid as a lubricant, and wherein means are provided on stationary gear bushings to facilitate distribution of the fluid to enhance the lubrication of the bearings.

A still further object of this invention is to provide flanged metal bearings for gear supporting bushings, wherein the bearings are spring loaded and O-ring sealed to the bushings.

Other objects, features and advantages of the invention will be apparent from the following detailed disclosure, taken in conjunction with the accompanying sheets of drawings, wherein like reference numerals refer to like parts, in 'which:

FIG. 1 is a perspective view of the gear pump of the present invention;

FIG. 2 is an exploded view of the pump of FIG. 1 showing the parts in perspective, but omitting the drive pulleys;

FIG. 3 is a front elevational view of the pump of FIG. 1;

FIG. 4 is a rear elevational view of the gear pump;

FIG. 5 is an enlarged transverse sectional view taken through the gear pump of the present invention, and substantially along line 55 of FIG. 3;

FIG. 6 is a greatly enlarged detail sectional view taken substantially along line 6-6 of FIG. 3;

FIG. 7 is a greatly enlarged fragmentary sectional View taken through one side of the gear pump and showing it modified with a liner, and illustrating the use of a support for a portion of the liner to be used during the molding process;

FIG. 8 is an enlarged detail view taken along a peripheral edge of a cavity and illustrating the O-ring group and O-ring arrangement normally employed when the body is constructed entirely of plastic;

FIG. 9 is a view similar to FIG. 8, but illustrating how the O-ring is formed when a liner is used in association with the plastic body;

FIG. is a greatly enlarged fragmentary view of a threaded section of a boss on one side of the pump and particularly illustrating how the liner is supported during the molding process and how a plastic lock is integrally formed along one thread of the boss;

FIG. ll is a more or less diagrammatic view of a system using the pump of the present invention in such a manner as to obtain a constant pressure use for release of pump speed;

FIG. 12 is an enlarged side elevational view of a drive gear bushing;

FIG. 13 is a transverse sectional view, taken substantially along line 13--13 of FIG. 12;

FIG. 14 is a rear elevational view of a bushing for an idler gear of the pump in the present invention;

FIG. 15 is a side elevational view of the bushing of FIG. 14, with a portion broken away to show the crosssectional configuration through one part thereof;

FIG. 16 is an enlarged side elevational view of an idler gear and particularly illustrating the grooves along the base of the teeth for preventing pressure lock during operation of the pump;

FIG. 17 is a transverse sectional view taken substantially along line 17-17 of FIG. 16;

FIG. 18 is a transverse view taken through an idler gear and bushing assembly having a modified bearing arrangement; and

FIG. 19 is an inside elevational View of the rear cover.

Referring now to the drawings, particularly to FIGS. 1 to 5, the gear pump of the present invention includes generally a body 20, a drive gear cartridge unit 21, an idler gear cartridge unit 22, a rear cover plate 23, a rear cover 24, a front cover 25, and a pulley 26.

The body 20 includes a base 27 for mounting the body to any suitable frame, and a generally upstanding housing 28. A pair of symmetrically formed generally circularly shaped cavitiesor bores 29 and 30 are provided in the housing 28 for receiving the drive and idler gear cartridge units. Because of the symmetrical formation of the cavities, the drive and idler gear units may be interchangeably positioned in either of the cavities. The merging of the cavities defines opposed inwardly projecting peaked portions 31 and 32, FIG. 2.

Extending from the opposite sides of the housing 28 and parallel to the longitudinal axes of the cavities are symmetrically formed extensions 33 and 34 having extending therethrough symmetrically formed passageways 35 and 36 which open to the opposite ends of the housing. The extensions are arranged between the upper and lower cavities. Arranged at the approximate midpoint of the extensions 33 and extending outwardly therefrom are bosses 37 and 38. The bosses as well as the extensions are also centrally arranged between the upper and lower cavities 29 and 30. The bosses 37 and 38 are respectively provided with bores 39 and 40 extending therethrough which function interchangeably as the inlet or outlet for the pump depending upon the driving of the gears. The bores are threaded at the outer ends to facilitate connecting lines to the pump when placing the pump into a pumping circuit. Further, the bores communicate with the cavities and intersect the passageways 35 and 36.

At each end of the pump, O-ring grooves 41 and 42 are provided around the passageways 35 and 36 for receiving O-rings 43 and 44 to seal against leakage of the fluid being pumped when the pump is assembled. Similarly, a continuous O-ring groove 45 is provided at each end of the housing about the cavities 29 and 30 for receiving a continuous O-ring 46 for preventing leakage of the fluid being pumped around the cavities.

As seen most particularly in FIGS. 2 and 5, the drive gear cartridge unit 21 includes a drive shaft 48 of steel, and preferably stainless steel, a drive gear 49, and op- A. posed bushings 50 which bearingly support the drive gear 49.

Although it may be appreciated that the parts of the pump of the present invention may be constructed of different types of material, it is shown herein and preferably constructed of basically a plastic. The satisfactory plastic material used is Du Ponts Delrin.

Accordingly, the drive gear 49 would be molded on the shaft 48, and includes opposed diametrically reduced bearing members 51 that may be separately molded and press fit on the shaft or integrally molded with the gear. Inasmuch as relatively engaging Delrin surfaces are not desirable because of insufficient wearing characteristics, sleeve type metal bearings of any suitable material and designated by the numeral 52 are provided on the bearing members 51 in press fit engagement therewith and are received in bearing bores 53 formed in the bushings 50. The bushings 50 are sized to fit within either of the cavities and support relative to the housing of the body the drive gear 49. A concave recess 54 is provided along the periphery of the bushings 50 as particularly seen in FIGS. 2 and 12, for reasons to be hereafter explained.

The idler gear cartridge unit includes an idler gear 55 and opposed bearing members 56. A longitudinal bore 57 extends through the idler gear and receives in press fit engagement therewith diametrically reduced portions 58 integral with the bearing members 56. Again to prevent the bearing engagement of the plastic material on plastic material, suitable metal bearing sleeves 59 are arranged in press fit engagement over the bearing members 56.

The front cover 25 is shaped to cover either end of the body 20 and to receive the shaft therethrough. The cover 25 is generally oblong in shape with opposed rounded ends, and provided with in alignment with the center of a cavity, a pair of stepped bosses 60 and 61 projecting therefrom. The boss 60 is hollow, as is the boss 61 to receive the shaft 48 and a suitable mechanical seal 62 to prevent leakage of fluid along the shaft and bosses. And a bore 63 is provided in an end wall 64 of the boss 61 to receive the shaft 48 which projects therefrom. The front cover 25 may be positioned with the bosses arranged in alignment with the cavity 29 or the cavity 30. Opposed extending enlargements 65 are provided on the front cover 25 to cover the respective open ends of the passageways 35 and 36 when the cover is in assembled position. Cap screws 66 are employed to secure the front cover to the body.

The rear cover plate in combination with the rear cover serves to cover one end of the body and close one end of the cavities, and further functions to provide a by-pass valve arrangement. The rear cover plate and rear cover are similarly shaped to fit with either end up, and on either end of the body 20. Particularly, the rear cover plate 23 may be constructed of metal, such as stainless steel, and shaped to cover both cavities 29 and 30 and the passageways 35 and 36 by means of wing portions 67 and 68 which are symmetrically formed on opposite sides along the center of the cover plate. Openings 67a and 68a are provided in the wings to align with the passageways 35 and 36 of the body 20 when the cover plate is assembled properly relative to the body.

The rear cover 24 is provided with a pair of bosses 69 and 70 extending laterally from opposite sides of the rear cover and projecting away from the face of the rear cover which engages the rear cover plate 23. Essentially, the bosses 69 and 70 define continuations of the extensions 33 and 34 on the body 20. The bosses 69 and 70 are respectively provided with hollows that define bores 71 and 72 which in elfect define extensions of the passageways 35 and 36 in the body 20. A parti-circular projection 73 extends from the rear cover 24 between the bosses 69 and 70 to define a substantially semi-circular in cross section recess 74 on the face of the rear cover which engages the rear cover plate 23, and thereby defines a channel or passageway 75 by coaction of the recess 74 in the rear cover plate 23 as seen in FIG. 5 and the rear cover plate 23 when the cover is in assembled position. The opposite ends of the recess 74 merge or open into the inner ends of the bores 71 and 72. A plurality of fasteners 76 are provided to secure the rear cover plate and rear cover to the body 20.

The channel 75 forms part of the by-pass circuit and intercommunicates the bores 71 and 72. A by-pass valve arrangement is provided in the bore 72 although it may just as well be provided in the bore 71 and comprises a pair of substantially identically formed, hat-shaped members 77 and 78 separated by a coil spring 79. As seen particularly in FIG. 6, the relatively hat-shaped members or buttons 77 and 78 include stepped cylindrical portions 77a and 77b, and 78a and 78b, respectively. The cylindrical sections 77a and 78a are larger than the cylindrical sections 77b and 78b and the members are arranged so that the smaller sections 77b and 78b are facing each other and received telescopically within the confines of the coil spring 79. The outer face 78c of the member 78 is flat and larger in cylindrical dimension than the opening 68a with which it aligns of the rear cover plate 23, as particularly seen in FIG. 6, and thereby defines a valve to selectively open and close the opening 68a and selectively intercommunicate it with the channel 75 in the rear cover under certain pressure conditions existing in the discharge side of the pump. The other face 770 of the member 77 is also fiat and is engaged by a threaded bolt 80 threadedly engaging in the end of the boss 70 and locked into position by a lock nut 81, whereby the by-pass pressure may be regulated depending upon the tension adjusted in the coil spring 79. The control bolt 80 may also function to shut off the by-pass by forcing the free end of the section 77b against the free end of the section 78b until the member 78 is locked tight into seated position against the rear cover p ate 23 to close off the opening 68a. The sections 7712 and 78b serve to center the spring in the bore 72. The diameter of the sections 77a and 78a of the buttons and the spring are sized to freely move in the bore 72. An O-ring groove 82, FIG. 19, is provided around the recess 74 and the bores 71 and 72 in the rear cover to receive an O-ring and to fluid seal the back cover portions with the rear cover plate 23.

Thus, the by-pass valve arrangement is simple and of a few number of parts, although it is capable of handling the full flow capacity of the pump with little noise and little heat rise. Further, no special machining need be performed for providing the proper valve seat and valve coaction. And because of the symmetry of the rear cover, the by-pass valve may be arranged at either side or either end of the pump according to the needs of the installation.

The pulley 26 is bearingly mounted on the boss 61, FIG. 5, and suitably coupled to the shaft. The pulley 26 is provided with a cylindrical recess 83 which receives in press fit engagement therewith a bearing 84 that is, in turn, in press fit engagement with the external surface of the boss 61. Although any type of pulley may be employed, a pulley having a pair of V-grooves of different dimensions is illustrated whereby varying speeds may be applied by shifting the belt to either of the grooves. A set screw 85 is threadedly received in a bore in the pulley and engageable with a fiat 48a on the shaft 48 for securing the pulley 26 to the shaft for corotation therewith. Accordingly, it may be appreciated that the loads applied to the pulley are absorbed through the bearing 84 and boss 61 and accordingly not transmitted to the shaft 48 to cause any misalignment of the shaft and malfunction of the pump. An annular chamber 86 is defined between the inner face of the recess in the pulley and the adjacent face of the end wall 64 to receive any leakage along the shaft. A slinger hole 87 intercommunicates the chamber 86 with the exterior of the pulley and will function to carry away any leakage thereby preventing it from'building up in the bearing and causing malfunctioning of the bearing by rust or the like.

Especially When constructing the pump of the present invention principally of plastic, in order to provide a proper fit between the front cover 25 and the body and prevent leakage at all points, generally circularly shaped reinforcing portions 87, FIGS. 3 and 6, are provided on the outer face of the cover in alignment with the wings 65 to function as reinforcing the wings and precluding the pressure exerted by the O-rings 43 and 44 from warping the cover and causing fluid leakage.

For some applications, it may be desired to have a lining of a particular material in the pump so that the liquids do not come in contact with the plastic. Specifically, it is a feature of this invention to provide a plastic bodied pump with a metal liner, and particularly stainless steel. Referring to FIG. 7, a metal liner 88 is shown in combination with a plastic body. In constructing the body 29 and having a metal liner, the liner is initially completely formed wherein the cavities, passageways and bores are connected into an integral structure, and a plastic body is molded therearound. Where a liner is employed, other changes in the construction are also necessary. For example, a metal liner would be provided for the recess 75 and the bores 71 and 72 of the rear cover 24, while a metal liner plate would be provided between the front cover and the body. Additionally, the gears and bearing mem bers or bushings would also by necessity be constructed of metal.

Moreover, such a liner for a pump could be made of ceramic, tantalum, or any other suitable material and arranged in an injection molding machine to be molded within the normal plastic body. Wherein a metal liner is provided and the plastic body is molded therearound, there would not be an O ring groove molded in the plastic equivalent to the O-ring groove 45 on each end of the body as particularly seen in FIG. 8. With the metal liner, only a notch 89, FIG. 9, need be provided to coact with the metal liner 88 and define an O-ring groove for the O-ring 46.

Further, it is proposed where a metal liner is provided and the body is molded therearound, that a slot be provided along one thread of the liner inlet and outlet ports, such as shown in FIGS. 7 and 10 and identified by the numeral 90 so that plastic would enter the port area in a thin annular band 91, FIG. 10, to provide a built in lock and seal when pipes, couplings, or hoses were screwed into the ports. Because the liner portion 92 would in all probability collapse during the injection molding process if not properly sup ported, a threaded pin 93 is positioned within the liner portion 92. The crest of the threads of the pin 93 are removed to define a relatively blunt end 94, as seen in FIG. 10, in order to accommodate and aid in defining the annular plastic portion 91 for locking and sealing purposes during the molding process.

When the bushings 59 are molded of plastic, and of Delrin, expansion thereof due to heat rise must be compensated for in order to prevent malfunctioning of the pump. Thus, to compensate for the expansion, annular grooves may be provided in the bushing, and as seen in FIGS. 12 and 13, an annular groove 95 is provided around the periphery of the bore 53 and for substantially the entire depth of the bushing. A second parti-annular groove 96 is provided concentric to the groove 95 and radially outwardly thereof. It should be appreciated that one or more of the grooves may be provided depending upon the size of the bushing and the need for compensating for the expansion while in operation. It should also be appreciated that the grooves 95 and 96 would extend inwardly from the outer face of the bushing remote from the face of the bushing which engages the ends of the gear teeth in order to prevent leakage of pumping fluids and undesirable action into the grooves.

Similarly, the bearing members 56 may be provided with annular grooves 97 to compensate for expansion of the member under temperature increase.

Referring again to FIGS. 12 and 13, the drive gear bushings 50 may be suitably grooved to provide lubrication on the dry surfaces and to prevent fluid entrapment and to drain the seal area of undesirable pressures. In order to accomplish these results, a pair of grooves 98 may be provided in the face of the concave recess 54 to allow the pumping fluid to flow between the opposite faces of the bushings 50 and along the width of the bearing surface on the bearing 56 which engages in the recess 54. A radially extending groove 99 may be provided on the opposite end faces of the bushings 50 to intercommunicate the surface of the bore 53 which is in engagement with the hearings on the drive gear and the bearing surface of the bearing members 56.

In order to prevent pressure lock between the teeth of the gears or provide liquid pressure relief, grooves 100 are provided along the base of the teeth, FIGS. 16 and 17, to intercommunicate along the opposite ends of the teeth the areas between the teeth. Although only the idler gear 55 is shown as having these grooves, it will be appreciated that the drive gear may be similarly provided with such grooves. Accordingly, any possibility of pressure lock between the teeth is alleviated.

Referring noW to FIG. 18, a modified form of bearingly mounting the idler gear in the body is shown wherein cup-shaped hearings or flanged sleeve bearings 101 are provided for the bearing members 56. In order to seal against fluid leakage between the bearing members 56 and the bearings 101 which are freely received on the bearing members, an O-ring groove and O-ring arrangement 102 are provided between the external surface of the bearing members 56 and the internal surface of the bearings 101. A plurality of coil springs 103 are received in recesses circumferentially arranged along the outer faces of the bearing members 56 and resiliently act against the flanges 104 of the bearing members 101 to urge the flanges into contact with the covers of the pump. This bearing arrangement increases the life and performance of the drive gear bearings. It may be appreciated that the drive gear bushing aligners may also likewise be spring and O-ring loaded to maintain contact on the ends with the covers to increase life and performance.

The pump of the present invention because of the bypass arrangement, may be used in a circuit for providing substantially constant pressure regardless of the speed of the pump over a predetermined range. An example of how the pump is connected into a circuit is shown in FIG. 11, wherein the pump, generally designated by the numeral 105, has its inlet 106 connected to a reservoir 107 and its outlet 108 connected to a line 109 which returns to the reservoir 107. A restricting valve 110 is provided in the line 109 along with a pressure gauge 111. It may .be noted that a pressure responsive valve 112 of the same construction as the by-pass arrangement shown in FIG. 6 is situated at the discharge end of the pump adjacent the outlet 108, and that a line or outlet 113 is connected to the boss opposite to the boss holding the valve 112 and opposite the inlet to the pump. A spray nozzle 114 may be connected to the line 113 if the liquid is to be used for spraying purposes. In operation, the pump is started and the restricting valve 110 is regulated to provide the desired pressure as read on the pressure gauge 111 which will open the pressure responsive valve and direct fluid under that pressure back toward the inlet 106 and out the line 113 to the spray nozzle 114. With the pressure responsive valve 112 operating a certain pressure, the regulating valve 110 is adjusted to provide a pressure in the line 109 above the operating pressure of the pressure responsive valve 112 to open same and to cause a discharge through line 113 and nozzle 114. The pump will deliver its sole discharge through valve until a back pressure in line 109 caused by the restriction of valve 110 is enough to begin overcoming the spring and the unloading valve 112. At this point the valve 112 will permit a small amount of flow through line 113. As the back pressure in line 109 continues to build up because of either an increase in pump speed or closing of valve 110, the unloading valve 112 will open further allowing a greater flow through line 113. The flow through line 113 will therefore be substantially proportional to the opening of valve 112 which is governed by the back pres sure in line 109, the latter being determined by pump speed and the sides of the opening of valve 110. It can therefore be seen that pump speed determines the flow through line 113. It is noted that the function of valve 112 is such that it tends to permit pressure to build up in line 109 to the point where it begins to unload. At this point the speed of the pump can continue to be increased and the pressure in line 109 will rise only slightly but not proportionately to pump speed since the unloading valve will begin to take a proportion of the flow from line 109. This condition will continue over a predetermined range of pump speed until valve 112 is fully open whereupon the flow through both lines 109 and 113 will be determined by and proportional to pump speed.

When connecting a plurality of pumps of the present invention in tandem, it will be appreciated that the drive gears and their hubs and the idler gears and their hubs or bushings may contain doweling or such driving members as will permit a successful tandem operation. Additionally, the bushings 50 may be enlarged in width in order to overlap cavities of adjacent pumps and thereby properly align the pumps together for proper operation.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention, but it is understood that this application is to be limited only by the scope of the appended claims.

The invention is hereby claimed as follows:

1. In a hydraulic circuit comprising a gear pump, said pump including a body having a pair of cylindrically shaped intersecting symmetrical cavities, a pair of bores, one extending through each side of said body substantially transverse the axes of the cavities and at the intersection thereof, said bores defining the inlet and outlet of said pump, a passageway at each side of the body extending substantially parallel to said cavities and intersecting a bore, a drive gear cartridge unit including a drive gear carried on a shaft and bearing supports bearingly mounting said drive gear and received in one of said cavities, an idler gear cartridge unit including an idler gear and bearing supports carrying said idler gear and bearingly received in the other of said cavities, a front cover secured to said body over one end of said cavities and said passageways and receiving the shaft therethrough, means sealing the shaft and front cover against fluid leakage along the shaft, a rear cover plate over the other end of the cavities, a rear cover over said cover plate and secured to the body, said rear cover having a channel, a pressure responsive valve in said channel at one end thereof, a reservoir of fluid, said pump inlet being connected to said reservoir, a line between the outlet and said reservoir, a restricting valve in the line, and a discharge outlet connected to said channel at the other end thereof, whereby a substantially constant fluid pressure discharge is maintained at the pump outlet regardless of the pump speed when the pressure in said line is within the operating pressure range of said pressure responsive valve.

2. A gear pump comprising a body having a pair of cylindrically shaped intersecting symmetrical cavities, a pair of bores one extending through each side of said body substantially transverse the axes of the cavities and at the intersection thereof, said bores defining the inlet and outlet of said pump, a passageway at each side of the body extending therethrough and substantially parallel to said cavities and intersecting a bore, said passageways being symmetrically positioned at the intersection of said cavities, a drive gear cartridge unit including a drive gear carried on a shaft and bearing supports bearingly mounting said drive gear and received in one of said cavities, an idler gear cartridge unit including an idler gear and bearing supports carrying said idler gear and bearingly received in the other of said cavities, said cartridge units being symmetrically formed for fitting in either of said cavities, a front cover secured to said body over one end of said cavities and said passageways and receiving the shaft therethrough, means coacting with said front cover, shaft and body for sealing fluid leakage along and between the shaft and said one ends of said cavities and passageways, said body and said front cover being so symmetrically formed as to be interchangeably mountable on either end of the cavities, a rear cover plate sealingly mounted on the body over the other end of the cavities, said rear cover plate being shaped substantially identical to the cross section of said body and closing the other ends of said cavities and having openings in alignment with the other ends of said passageways, a rear cover over said cover plate and secured to the body, said rear cover plate and said rear cover being so symmetrically formed as to be interchangeably mountable on either ends of the cavities, said rear cover having a pair of spaced blind bores in the side facing the rear cover plate and in alignment with the openings therein, a recess in the side of the rear cover facing the rear cover plate and extending between said blind bores for intercommunicating same, said recess coacting with said rear cover plate to define a by-pass channel extending parallel to said bores and in communication at opposite ends with said passageways, and a by-pass valve member in one of said blind bores normally blocking passage of fluid through said by-pass channel by engaging said rear cover plate and covering the aligned opening therein and responding to pump pressure at said outlet to selectively intercommunicate said outlet with said inlet.

3. A gear pump comprising a body having a pair of cylindrically shaped intersecting symmetrical cavities, a pair of bores one extending through each side of said body substantially transverse the axes of the cavities and at the intersection thereof, said bores defining the inlet and outlet of said pump, a passageway at each side of the body extending therethrough and substantially parallel to said cavities and intersecting a bore, said passageways being symmetrically positioned at the intersection of said cavities, a drive gear cartridge unit including a drive gear with a plurality of gear teeth carried on a shaft and bearing supports bearingly mounting said drive gear and received in one of said cavities, an idler gear cartridge unit including an idler gear with a plurality of gear teeth and bearing supports carrying said idler gear and bearingly received in the other of said cavities, said cartridge units being symmetrically formed for fitting in either of said cavities, a front cover secured to said body over one end of said cavities and said passageways and receiving the shaft therethrough, means coacting with said front cover, shaft and body for sealing fluid leakage along and between the shaft and said one ends of said cavities and passageways, said body and said front cover being so symmetrically formed as to be interchangeably mountable on either end of the cavities, a rear cover plate sealingly mounted on the body over the other end of the cavities, said rear cover plate being shaped substantially identical to the cross section of said body and closing the other ends of said cavities and having openings in alignment with the other ends of said passageways, a rear cover over said cover plate and secured to the body, said rear cover plate and said rear cover being so symmetrically formed as to be interchangeably mountable on either ends of the cavities, said rear cover having a by-pass channel extending along the side facing the cover plate, said channel extending parallel to said bores to coact therewith and intercommunicate said other ends of said passageways, and a one-Way by-pass valve normally blocking said channel and responding to pump pressure at said outlet to selectively intercommunicate said outlet with said inlet.

4. The gear pump defined in claim 3, wherein the pressure responsive valve is adjustable.

5. The gear pump as defined in claim 3, and a groove at each end of each gear tooth and along the base thereof defining with the adjacent bearing supports channels between each adjacent pair of gear teeth to prevent pressure lock between the teeth.

6. The gear pump as defined in claim 3, wherein said bearing supports of said cartridge units are of molded plastic, and an annular groove in each of said bearing supports to compensate for expansion caused by temperature rise.

7. The gear pump as defined in claim 3, wherein said drive gear is secured to said shaft and provided with axially extending cylindrical bearings at opposite sides thereof, said bearings having a substantially smaller diameter than said drive gear, said drive gear bearing supports being cylindrical and having bores extending therethrough for receiving the bearings of said drive gear, an arcuate cutout along the periphery of said bearing supports defining a parti-cylindrical surface, said idler gear bearing supports being cylindrical and mating with the particylindrical surface of said drive gear bearing supports, and transversely extending grooves along the entire particylindrical surface of each drive gear bearing support to provide lubrication thereof and prevent fluid entrapment.

8. The gear pump as defined in claim 3, wherein said idler gear is provided with an axial bore, and said bearing supports therefor having first and second cylindrical portions, said first cylindrical portion being sized substantially equal to the diameter of the gear and said second cylindrical portion being sized slightly larger than the diameter of the idler gear bore and press fitted therein.

9. The gear pump as defined in claim 3, wherein said idler gear is provided with an axial bore, and said bearing supports therefor having first and second cylindrical portions, said first cylindrical portion being sized slightly less than the diameter of said gear and arranged adjacent one side of the gear and said second cylindrical portion being sized slightly larger than the diameter of the idler gear bore and press fitted therein, a bearing member on each bearing support including a sleeve portion freely received on each first cylindrical portion and an annular flange normal to said sleeve portion and arranged on the free end of said first cylindrical portion, spring biasing means between said first cylindrical portion and said flange portion, and O-ring gasketing between the sleeve portion and the adjacent surface of the first cylindrical portion.

10. The gear pump as defined in claim 3, said gear cartridge units being of metal, said body including a metal liner extending through said cavities, bores and passage- Ways and a plastic shell molded therearound, said front cover being of molded plastic, a metal plate between said front cover and said body for covering the corresponding ends of said cavities, said rear cover plate being of metal, and said rear cover being of molded plastic and having a metal liner in the by-pass channel.

11. The gear pump as defined in claim 10, wherein said liner in the cavities terminates at the opposite ends of the cavities substantially flush with the plastic shell, and a notch formed along the periphery of the cavities coacting with the liner to define an O-ring groove.

12. The gear pump as defined in claim 10, wherein the liner extending through the bores is threadedly formed, a slot in the threaded portion of the liner along the crest of one thread, and a line of plastic extending through said slot defining a locking and sealing member when engaged by a fitting.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Kiefer July 14, 1914 Lent et al Apr. 7, 1925 McIntyre Dec. 16, 1930 Waterous et a1 Sept. 3, 1935 Seyvertsen Oct. 25, 1938 Svenson Jan. 30, 1940 Patton Apr. 7, 1942 Pugh Dec. 18, 1945 Taylor Dec. 20, 1949 Weeks June 10, 1952 Maisch Nov. 25, 1952 Funk Apr. 28, 1953 

2. A GEAR PUMP COMPRISING A BODY HAVING A PAIR OF CYLINDRICALLY SHAPED INTERSECTING SYMMETRICAL CAVITIES, A PAIR OF BORES ONE EXTENDING THROUGH EACH SIDE OF SAID BODY SUBSTANTIALLY TRANSVERSE THE AXES OF THE CAVITIES AND AT THE INTERSECTION THEREOF, SAID BORES DEFINING THE INLET AND OUTLET OF SAID PUMP, A PASSAGEWAY AT EACH SIDE OF THE BODY EXTENDING THERETHROUGH AND SUBSTANTIALLY PARALLEL TO SAID CAVITIES AND INTERSECTING A BORE, SAID PASSAGEWAYS BEING SYMMETRICALLY POSITIONED AT THE INTERSECTION OF SAID CAVITIES, A DRIVE GEAR CARTRIDGE UNIT INCLUDING A DRIVE GEAR CARRIED ON A SHAFT AND BEARING SUPPORTS BEARINGLY MOUNTING SAID DRIVE GEAR AND RECEIVED IN ONE OF SAID CAVITIES, AN IDLER GEAR CARTRIDGE UNIT INCLUDING AN IDLER GEAR AND BEARING SUPPORTS CARRYING SAID IDLER GEAR AND BEARINGLY RECEIVED IN THE OTHER OF SAID CAVITIES, SAID CARTRIDGE UNITS BEING SYMMETRICALLY FORMED FOR FITTING IN EITHER OF SAID CAVITIES, A FRONT COVER SECURED TO SAID BODY OVER ONE END OF SAID CAVITIES AND SAID PASSAGEWAYS AND RECEIVING THE SHAFT THERETHROUGH, MEANS COACTING WITH SAID FRONT COVER, SHAFT AND BODY FOR SEALING FLUID LEAKAGE ALONG AND BETWEEN THE SHAFT AND SAID ONE ENDS OF SAID CAVITIES AND PASSAGEWAYS, SAID BODY AND SAID FRONT COVER BEING SO SYMMETRICALLY FORMED AS TO BE INTERCHANGEABLY MOUNTABLE ON EITHER END OF THE CAVITIES, A REAR COVER PLATE SEALINGLY MOUNTED ON THE BODY OVER THE OTHER END OF THE CAVITIES, SAID REAR COVER PLATE BEING SHAPED SUBSTANTIALLY IDENTICAL TO THE CROSS SECTION OF SAID BODY AND CLOSING THE OTHER ENDS OF SAID CAVITIES AND HAVING OPENINGS IN ALIGNMENT WITH THE OTHER ENDS OF SAID PASSAGEWAYS, A REAR COVER OVER SAID COVER PLATE AND SECURED TO THE BODY, SAID REAR COVER PLATE AND SAID REAR COVER BEING SO SYMMETRICALLY FORMED AS TO BE INTERCHANGEABLY MOUNTABLE ON EITHER ENDS OF THE CAVITIES, SAID REAR COVER HAVING A PAIR OF SPACED BLIND BORES IN THE SIDE FACING THE REAR COVER PLATE AND IN ALIGNMENT WITH THE OPENINGS THEREIN, A RECESS IN THE SIDE OF THE REAR COVER FACING THE REAR COVER PLATE AND EXTENDING BETWEEN SAID BLIND BORES FOR INTERCOMMUNICATING SAME, SAID RECESS COACTING WITH SAID REAR COVER PLATE TO DEFINE A BY-PASS CHANNEL EXTENDING PARALLEL TO SAID BORES AND IN COMMUNICATION AT OPPOSITE ENDS WITH SAID PASSAGEWAYS, AND A BY-PASS VALVE MEMBER IN ONE OF SAID BLIND BORES NORMALLY BLOCKING PASSAGE OF FLUID THROUGH SAID BY-PASS CHANNEL BY ENGAGING SAID REAR COVER PLATE AND COVERING THE ALIGNED OPENING THEREIN AND RESPONDING TO PUMP PRESSURE AT SAID OUTLET TO SELECTIVELY INTERCOMMUNICATE SAID OUTLET WITH SAID INLET. 